Answer:
Wait – please be careful!
Those plans you have are only to show you that there is a presence of underground utilities within the area. Some plans may have offsets and depths shown on them, but others – especially Telstra, NBN and Optus – will only be a schematic drawing and should not be used to scale off or even rely upon without experience in reading them.
For your own peace of mind we’d strongly recommend you still get a cable locator out to site, to ensure you’re safe and nothing gets damaged.